Parasites. When most people think of a parasite, it often brings to mind images of worm-like creatures infesting other animals. While that is one correct perception, there is a lot more to these creatures than most commonly imagine.
So what exactly counts as a parasite? A parasite is anything that lives in or on another organism (the host) and benefits by deriving nutrients at the host’s expense without providing the host with anything for compensation. Due to this fairly broad definition, parasites appear in many different ways, shapes, and forms. Despite parasites having a bad rap, their goal is not to kill their host. Without a host, the parasites will not survive either.
A parasitic relationship is a form of symbiosis - or a long-term interaction between two organisms. There are three main kinds of symbiosis: mutualism, commensalism, and parasitism. Mutualism is a relationship between organisms where both individuals benefit from the interaction. An example of this kind of relationship is between microbes that live in our intestines and us. They help us digest food and we provide a safe environment in which they can live. Commensalism describes a relationship when one organism benefits from an interaction while the other is not significantly affected - either positively or negatively. Parasitism, as we mentioned above, is a version of symbiosis where one organism benefits and the other is harmed.
Parasites live in almost every environment, even in Colorado! However, as is the case for many other organisms, the high altitude limits the number of parasites that reside here. A prime example of this phenomenon is the tick. A common parasite found across the country, one will not encounter very many while hiking in Colorado in the summer. A parasite known by most, ticks are small arachnids (the same group of animals that spiders are a part of) that bite their host and feed on the blood of the organism for a few days before falling off. One reason they get a lot of attention is because they often carry diseases that are transmitted to the host organism when they bite. While there are only two main kinds of ticks in Colorado that bite humans, there are more than 30 other species that are found in the area, but prefer other organisms. Another bright side to living up here? The ticks that are found in this area do not carry the well-known Lyme disease. No officially reported human case of the disease has ever originated in Colorado.
Another reason ticks are well known is because we can see them with our bare eyes. However, the world of parasites often takes place at the microscopic level. One of these common microscopic parasites is giardia. And guess what? You have the potential of encountering giardia every day. Giardia is a unicellular, flagellated protozoan that inhabits the small intestines of animals, including humans. Giardia is transmitted through contaminated dirt, water, and other surfaces. They can survive outside of a host for months waiting for another host to consume them. The most common way of coming in contact with this parasite is through drinking unclean water - even eating snow can do the trick. So what happens when you ingest this parasite? Sometimes nothing. But more commonly, the host develops a condition called giardiasis which is an unpleasant infection of the intestinal tract. Enough said.
These are just a few glimpses into the vast world of parasites - a type of organism that is just trying to find its own way to survive. Ticks and their parasite kin might be gross, but ultimately, they are just another example of what a complex and interesting world we live in.
Laura Robison is a Naturalist at Walking Mountains Science Center in Avon. She is fascinated by the diversity of strategies that organisms have developed to live on this Earth.
